Color stabilization of aromatic polycarbonates was hitherto preferably effected by adding additives, in particular phosphites (compare DT-AS (German published specification) No. 1,128,653 (Le 1,926), DT-AS (German published specification) No. 2,140,207, (LeA 13,917) which corresponds to U.S. Pat. No. 3,794,629 and DT-OS (German published specification) No. 2,255,639 (LeA 14,709) which corresponds to U.S. Pat. No. 4,073,769), optionally in combination with other additives, such as, for example with oxethane compounds (DT-OS (German published specification) No. 2,510,463 (LeA 16,231).
Compared with these methods for color stabilization of polycarbonates, the method according to the invention uses a completely different principle in that cyclic aza compounds are used as catalysts in the preparation of polycarbonates by the two-phase boundary polycondensation process (compare German patent specification No. 959,497 (Le 1,693), German patent specification No. 1,046,311 (Le 1,747) and German patent specification No. 2,410,716 (LeA 15,514) which corresponds to U.S. Pat. No. 4,038,252).